1. Field of the Invention
This invention relates to an improvement in a leader tape or trailer tape for a magnetic tape and more particular, it is concerned with a novel structure of a leader tape or trailer tape situated at the head portion or tail portion or, if necessary, intermediate portion of a long tape for magnetic recording such as video tapes, memory tapes or audio tapes.
2. Description of the Prior Art
Up to the present time, it has been considered that the phenomenon of drop out occurring in a magnetic tape section is a problem of the magnetic tape itself and is scarcely related with the leader tape. However, it is found by our studies that the drop outs increasing in a magnetic tape during running or occurring in the head of a magnetic tape during repeated use are governed by the properties of the leader tape and that the properties of not only the coated side but also the reverse side are important. When a magnetic tape is loaded in a cassette having a fixed guide pin with an acute tape winding angle, such a phenomenon that the magnetic tape sticks fast to the fixed guide pin and rewinding thereof is impossible occurs often in a leader of the prior art. Now it is found that this phenomenon is due to the leader and not due to the magnetic tape. That is to say, it is considered that if the leader has not suitable properties, the magnetic tape or guide system is contaminated, thus resulting in increasing of drop outs and poor results in rewinding of the magnetic tape. Furthermore, this causes scratching and scraping of the coating layer or base side.
As to such a leader tape or trailer tape, there have hitherto been proposed various proposals, for example, comprising (1) providing a metallic vapor deposition film in the form of a stripe (Japanese Utility Model Publication No. 14349/1971), (2) matting the one side or both sides of a base (Japanese Utility Model Publication No. 42726/1974) and (3) providing a coating layer containing 50 to 800 parts of a pigment having a grain size of 4 microns or less per 100 parts of a binder (Japanese Patent Application (OPI) Nos. 40504/1974 and 67603/1974). Above all, the method (3) is more preferable, but still has the following disadvantages: (1) The coating film is spoiled by a tape running system including a guide pole and magnetic head during repeated use, resulting in increase of drop outs and instability of the tape running property. (2) Dusts adhere to the end of a video head revolving at a high speed as in a helical VTR, resulting in clogging, and consequently, recording or reproducing of video signals becomes difficult. (3) The friction coefficient of the leader is increased at a high temperature and high humidity so that it is difficult to keep a required constant running speed and the tape running property is unstable. (4) The running property gets worse with the increase of the tape winding angle at rewinding.